无法在asp.net的下拉列表中显示选定的值

Question

我有一个下拉列表，我可以看到列表项从1到10，但是当我选择任何一个不显示在下拉列表中的值时，

<asp:DropDownList ID="ddlqty" runat="server" CssClass="myselect">
    <asp:ListItem Value="1" Selected="True">1</asp:ListItem>
    <asp:ListItem Value="2">2</asp:ListItem>
    <asp:ListItem Value="3">3</asp:ListItem>
    <asp:ListItem Value="4">4</asp:ListItem>
    <asp:ListItem Value="5">5</asp:ListItem>
    <asp:ListItem Value="6">6</asp:ListItem>
    <asp:ListItem Value="7">7</asp:ListItem>
    <asp:ListItem Value="8">8</asp:ListItem>
    <asp:ListItem Value="9">9</asp:ListItem>
    <asp:ListItem Value="10">10</asp:ListItem>
</asp:DropDownList>

我在这里想念什么。 同样在intellisense后面的代码中没有得到ddlqty ，这是下拉列表的ID。

这是我从浏览器中获取的HTML：

 <select name="Repeater1$ctl01$ddlqty" id="Repeater1_ddlqty_0" class="myselect">
<option selected="selected" value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
<option value="6">6</option>
<option value="7">7</option>
<option value="8">8</option>
<option value="9">9</option>
<option value="10">10</option>

我的Repeater班

<asp:Repeater ID="Repeater1" runat="server">
    <HeaderTemplate></HeaderTemplate>
    <ItemTemplate>
        <tr class="cart_item">
            <td class="product-thumbnail">
                <a href="#">
                    <img src=" images/ecommerce/products/hoodie_1_front-150x150.jpg" alt=""></a>
            </td>
            <td class="product-name"><a href="#"><%#Eval("ItemName") %></a>
                <dl class="variation">
                    <dt class="variation-Color">Category:</dt>
                    <dd class="variation-Color">
                        <p><%#Eval("Category") %></p>
                    </dd>
                </dl>
            </td>
            <td class="product-price"><span class="amount"><%#Eval("Rate") %></span></td>
            <td class="product-quantity">
                <%-- <a href="#" class="minus disabled">-</a>
                                    <input type="text" value="1"> <a href="#" class="plus">+</a></td>--%>
                <%--<input type="text" value="1" readonly="true">--%>

                <asp:DropDownList ID="ddlqty" runat="server" CssClass="myselect">
                    <asp:ListItem Value="1" Selected="True">1</asp:ListItem>
                    <asp:ListItem Value="2">2</asp:ListItem>
                    <asp:ListItem Value="3">3</asp:ListItem>
                    <asp:ListItem Value="4">4</asp:ListItem>
                    <asp:ListItem Value="5">5</asp:ListItem>
                    <asp:ListItem Value="6">6</asp:ListItem>
                    <asp:ListItem Value="7">7</asp:ListItem>
                    <asp:ListItem Value="8">8</asp:ListItem>
                    <asp:ListItem Value="9">9</asp:ListItem>
                    <asp:ListItem Value="10">10</asp:ListItem>
                </asp:DropDownList>

                <%--<asp:LinkButton ID="LinkButton1" runat="server" CausesValidation="false" CommandName="Edit" Text="Change" Font-Size="Small"></asp:LinkButton>--%>
                <td class="product-subtotal"><span class="amount">$ <%#Eval("Rate") %></span></td>
                <td class="product-remove"><a href="#" class="remove"><i class="fa fa-times"></i></a></td>
        </tr>
    </ItemTemplate>
    <FooterTemplate></FooterTemplate>
</asp:Repeater>

请帮忙

Answer 1

当控件位于中继器中时，您不能直接访问它。 您将必须使用FindControl ，并将其包含在Repeater中的包含控件的Item的索引号中。

DropDownList drp = Repeater1.Items[index].FindControl("ddlqty") as DropDownList;
drp.SelectedValue = "2";

更新

如果要从购物车设置DropDownList值，并在更改项目时更新购物车，则可以通过添加OnItemDataBound和OnSelectedIndexChanged

<asp:Repeater ID="Repeater1" runat="server" OnItemDataBound="Repeater1_ItemDataBound">
    <ItemTemplate>
        <asp:DropDownList ID="ddlqty" runat="server" OnSelectedIndexChanged="ddlqty_SelectedIndexChanged" AutoPostBack="true">
            <asp:ListItem Value="1">1</asp:ListItem>
            <asp:ListItem Value="2">2</asp:ListItem>
            <asp:ListItem Value="3">3</asp:ListItem>
        </asp:DropDownList>
        <asp:Label ID="Label1" runat="server" Text='<%# Eval("tocht_id") %>' Visible="false"></asp:Label>
    </ItemTemplate>
</asp:Repeater>

后面的代码

protected void Repeater1_ItemDataBound(object sender, RepeaterItemEventArgs e)
{
    int itemsInCart = 3;

    //find the dropdownlist using findcontrol
    DropDownList drp = e.Item.FindControl("ddlqty") as DropDownList;

    //set the correct cart value
    drp.SelectedValue = itemsInCart.ToString();
}

protected void ddlqty_SelectedIndexChanged(object sender, EventArgs e)
{
    //cast the sender back to a dropdownlist
    DropDownList drp = sender as DropDownList;

    //get the item as a repeater item
    RepeaterItem item = drp.NamingContainer as RepeaterItem;

    //find the label with the product ID in the Repeater
    Label lbl = Repeater1.Items[item.ItemIndex].FindControl("Label1") as Label;

    //get the product id from the attri
    int productID = Convert.ToInt32(lbl.Text);

    //convert the selectedvalue back to an int
    int itemsInCart = Convert.ToInt32(drp.SelectedValue);

    //you now have the product id and the new cart amount
}

Answer 2

尝试使用foreach循环获取DropDownList值

foreach(RepeaterItem item in rpt1.Items)
{
   DropDownList ddl = (DropDownList)item.FindControl("ddl");
   string ddl_value = ddl.SelectedValue;               
}

注意：rpt1是中继器的ID

还请注意，通过使用foreach loop您将获得所有dropdownlist's值，因此您必须根据自己的情况使用它。

Answer 3

以下是在页面加载事件下IsPostback条件下用于在页面加载时绑定转发器的代码

 private void BindData()
        {
            DataTable dt = new DataTable();
            dt.Columns.Add("ID", Type.GetType("System.String"));
            dt.Columns.Add("ItemName", Type.GetType("System.String"));
            dt.Columns.Add("Category", Type.GetType("System.String"));
            dt.Columns.Add("Rate", Type.GetType("System.String"));
            dt.Columns.Add("Qty", Type.GetType("System.String"));
            dt.Columns.Add("Total", Type.GetType("System.String"));
            for (int i = 1; i <= 10; i++)
            {
                DataRow dr = dt.NewRow();
                dr["ID"] = 1;
                dr["ItemName"] = "hoodie";
                dr["Category"] = "Hoodie";
                dr["Rate"] = 25;
                dr["Qty"] = 4;
                dr["Total"] = (4 * 25);
                dt.Rows.Add(dr);
            }
            Repeater1.DataSource = dt;
            Repeater1.DataBind();
        }



        protected void Repeater1_ItemDataBound(object sender, RepeaterItemEventArgs e)
        {
            if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
            {
                DropDownList ddlQty = new DropDownList();
                ddlQty = (DropDownList)e.Item.FindControl("ddlqty");
                HiddenField hdn = new HiddenField();
                hdn = (HiddenField)e.Item.FindControl("hdnQty");
                if (hdn.Value != "")
                {
                    ddlQty.SelectedItem.Selected = false;
                    ddlQty.Items.FindByValue(hdn.Value).Selected = true;
                }
            }
        }

您需要使用Repeater的ItemDataBound事件，该事件将在将数据绑定到Repeater时为您提供控件，并且可以在绑定记录时更改该控件的值。

您要做的另一件事是处理下拉索引事件，该事件将为您提供qty的值，您可以使用它重新绑定转发器。

Answer 4

我能够解决我的问题，现在我可以在下拉列表的文本中看到选定的值。 但是，我必须删除Repeater 。 并改为使用gridview。 我有1个问题是，当我点击Save使用<asp:LinkButton ID="lnkUpdate" runat="server" CommandName="Update" Text="Save" ></asp:LinkButton>再次刷新页面和值变为1，这是默认值。 这是我的代码：

 <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" CellPadding="4" DataKeyNames="slno" ForeColor="#333333" GridLines="None" HorizontalAlign="Center" Width="100%" OnRowEditing="GridView1_RowEditing" OnRowCancelingEdit="GridView1_RowCancelingEdit" OnRowUpdating="GridView1_RowUpdating">
     <RowStyle HorizontalAlign="Center" VerticalAlign="Middle" BackColor="#F7F6F3" ForeColor="#333333" />
      <Columns>
      <asp:BoundField DataField="slno" HeaderText="Sl No" ReadOnly="true">
         <HeaderStyle HorizontalAlign="Center" VerticalAlign="Middle" />
           <ItemStyle HorizontalAlign="Center" VerticalAlign="Middle" />
      </asp:BoundField>
      <asp:BoundField DataField="itemname" HeaderText="Item Name" ReadOnly="true">
         <HeaderStyle HorizontalAlign="Left" VerticalAlign="Middle" />
           <ItemStyle HorizontalAlign="Left" VerticalAlign="Middle" />
      </asp:BoundField>
     <asp:BoundField DataField="Rate" HeaderText="Price" ReadOnly="true">
         <HeaderStyle HorizontalAlign="Center" VerticalAlign="Middle" />
           <ItemStyle HorizontalAlign="Center" VerticalAlign="Middle" />
     </asp:BoundField>
  <asp:TemplateField HeaderStyle-CssClass="headerStyle" HeaderText="Quantity">
     <EditItemTemplate>
         <asp:DropDownList ID="ddlqty" runat="server" DataTextField='<%# Bind("qty") %>' AutoPostBack="false" EnableViewState="true">

             <asp:ListItem>1</asp:ListItem>

             <asp:ListItem>2</asp:ListItem>

             <asp:ListItem>3</asp:ListItem>

             <asp:ListItem>4</asp:ListItem>

             <asp:ListItem>5</asp:ListItem>
                                                                                                                 </asp:DropDownList>
   </EditItemTemplate>

   <ItemTemplate>
     <asp:Label ID="lblqty" runat="server" Text='<%# Bind("qty") %>'></asp:Label>
   </ItemTemplate>

   <HeaderStyle CssClass="headerStyle" HorizontalAlign="Center" VerticalAlign="Middle" />
     <ItemStyle HorizontalAlign="Center" VerticalAlign="Middle" />
</asp:TemplateField>
   <asp:TemplateField HeaderStyle-CssClass="headerStyle">
                                                <EditItemTemplate>
                                                    <asp:LinkButton ID="lnkUpdate" runat="server" CommandName="Update" Text="Save" ></asp:LinkButton>
                                                    <%--<asp:LinkButton ID="lnkCancel" runat="server" CommandName="Cancel" Text="Cancel"></asp:LinkButton>--%>
                                                </EditItemTemplate>
                                                <ItemTemplate>
                                                    <asp:LinkButton ID="LinkButton1" runat="server" CausesValidation="false" CommandName="Edit" Text="Change"></asp:LinkButton>
                                                </ItemTemplate>
                                                <HeaderStyle CssClass="headerStyle" />
                                                <ItemStyle HorizontalAlign="Center" Width="30px" Font-Size="Small" />
                                            </asp:TemplateField>
                                            <asp:BoundField DataField="total" HeaderText="Total" ReadOnly="true">
                                                <HeaderStyle HorizontalAlign="Right" VerticalAlign="Middle" />
                                                <ItemStyle HorizontalAlign="Right" VerticalAlign="Middle" />
                                            </asp:BoundField>
                                        </Columns>
                                        <EditRowStyle HorizontalAlign="Center" VerticalAlign="Middle" BackColor="#999999" />
                                        <FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
                                        <PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />
                                        <SelectedRowStyle BackColor="#E2DED6" ForeColor="#333333" Font-Bold="True" />
                                        <HeaderStyle BackColor="#5D7B9D" Font-Bold="True" HorizontalAlign="Center" VerticalAlign="Middle" ForeColor="White" />
                                        <AlternatingRowStyle BackColor="White" ForeColor="#284775" />
                                        <SortedAscendingCellStyle BackColor="#E9E7E2" />
                                        <SortedAscendingHeaderStyle BackColor="#506C8C" />
                                        <SortedDescendingCellStyle BackColor="#FFFDF8" />
                                        <SortedDescendingHeaderStyle BackColor="#6F8DAE" />
                                    </asp:GridView>

我以前有一个朋友和我一起做过一个项目，所以用了他的代码。